Planetary nodes and apses in the Sūrya-Siddhānta

Abstract

There are a few aspects of Indian astronomy that border on the implausible, and none more so than the nodal and apsidal movements of planetary orbits as specified in the Sūrya-Siddhānta. In this paper we examine some aspects of this data in the light of modern astronomy. Given the very-slow rates of motion specified for these two parameters, we speculate that this data might be heliocentric (as opposed to geocentric), and proceed with that assumption in this paper. It is determined that while this assumption proves true for the outer planets (Mars, Jupiter and Saturn), it does not conform well with the inner planets (Mercury and Venus). It is also determined that while the directions specified in the Sūrya-Siddhānta for these subtle motions are correct, the rates of motion given are slower by a couple orders of magnitude compared to actuality. Further analysis also appears to confirm that the data is genuine, and the epoch of the data is likely many thousands of years old.